O2 sensor Wrong?

My 97 4.0 ranger had a O2 sensor code problem. Previous owner had did some welding on the exhaust without removing the sensors. So I replace them with JY ones I got off an Explorer. Both O2 sensor are the upper bank ones. When I replace them I have the gray connectors. The ones off the Explorer were green. So of swap connectors and install the O2. I still get the same codes. Could it be I have the wrong sensors?

What is the exact code number?

You could just have a blown fuse for the Heated portion of the O2 sensor.

O2 sensors are all pretty much the same as far as the sensor voltage output, only the wiring on the connector might be different.

Ranger and Explorer should have the same wiring on O2s but I would look up wiring diagrams by Year to make sure, you didn't mention the Year of the Explorer(donor)

Heat from welding near the O2 probably wouldn't bother it, O2s don't even start working until they are above 650degF, but the soot from welding can coat sensor and make it less accurate, which is also why "running rich" can ruin an O2 sensor.
Heat from welding can bother near by wiring

RonD said:

What is the exact code number?

You could just have a blown fuse for the Heated portion of the O2 sensor.

O2 sensors are all pretty much the same as far as the sensor voltage output, only the wiring on the connector might be different.

Ranger and Explorer should have the same wiring on O2s but I would look up wiring diagrams by Year to make sure, you didn't mention the Year of the Explorer(donor)

Heat from welding near the O2 probably wouldn't bother it, O2s don't even start working until they are above 650degF, but the soot from welding can coat sensor and make it less accurate, which is also why "running rich" can ruin an O2 sensor.
Heat from welding can bother near by wiring

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I don't know what year the Explorers were. I guessing around 97-2000. They where both on the upper bank just like the Ranger and both where from 4.0 motors. I do know I have a problem with a fuse that blows once you put in a replacement. It goes to the cigarette power outlet. It will pop a 25amp fuse and its only suppose to have a 7.5amp fuse. I don't know if that is the power circuit for the O2's. Will have to go to the library and look it up in the repair manual. I do know its affecting running in the morning. Makes the car very cold nature.

Tested O2's

I did ohm test the sensor before installing them and they check out ok. So don't know what else if could be. Really don't want to purchase new O2's just to find out it didn't make a difference.

Doesn't welding also potentially introduce some fairly high current into wiring? (Assuming an electric welder was used.)

Do you remember the code number?
There really is no code for bad O2

Usually O2 is showing rich or lean, which is another problem being detected by the O2 sensors, so they are doing their job, i.e. "don't shoot the messenger"

Cigarette lighter fuse is suppose to be 25amp #17

HO2 fuse should be #20 in engine Fuse box, 15Amp, but check the lid for labels
HO2 = Heated O2


No difference in upstream or downstream O2 sensors, they are interchangeable.
If you are picking used parts always go for the downstream O2s, they only see "cleaned" exhaust being after the Cat converter, these tend to last the life of the vehicle vs the 100k mile recommended change time for upstream O2s.

Good stuff

Thanks RonD...that is good info. Thanks for the help. I'll check it out and see if that fuse is blown.

Codes

RonD said:

Do you remember the code number?
There really is no code for bad O2

Usually O2 is showing rich or lean, which is another problem being detected by the O2 sensors, so they are doing their job, i.e. "don't shoot the messenger"

Cigarette lighter fuse is suppose to be 25amp #17

HO2 fuse should be #20 in engine Fuse box, 15Amp, but check the lid for labels
HO2 = Heated O2


No difference in upstream or downstream O2 sensors, they are interchangeable.
If you are picking used parts always go for the downstream O2s, they only see "cleaned" exhaust being after the Cat converter, these tend to last the life of the vehicle vs the 100k mile recommended change time for upstream O2s.

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Ok I just read the codes again. The main ones I get are;
P0135 O2 Sensor Heater Circuit Bank 1 Sensor
P0141 O2 Sensor Heater Circuit Bank 1 Sensor
P0155 O2 Sensor Heater Circuit Bank 2 Sensor
Those are the ones that keep popping up.

But this time I read them I got more codes. I have a problem if I let it idle for a period of time it will start to chug and run rough to the point it will cut off. Even if I give it gas it will try and cut off. Like if I am in the pick up line at school its hard to keep it running.

P1150 Manufacture Control, P1151 Manufacture Control, P0171 System too Lean Bank, P0174 System too Lean Bank 2, P0004 Fuel volume Regulator Control Circuit High, and Multiple Cylinder missfire 1,2,3.

I did find a fuse blown in the engine fuse block. Mini fuse#3 15 amp. Replace it and cleared my codes. Will find out in the morning on a cold start if the problem goes away. I didn't see a #20 fuse that you talk about. I look on the cover.

Thats the fuse

I found a fuse diagram of the engine fuse block. And #20 is the third mini fuse. You be the ManI hope that is all it is. Now for the other codes I hope that fixes them too. Have to wait and see. So when he used his electrical welder it must have blown that fuse. Go figure. Would have ever thought about that.

The upstream and downstream sensors are not always interchangable. The 2002+ 4.0 SOHC sensors operate in different ranges, and a downstream sensor installed in an upstream hole causes problems.

adsm08 said:

The upstream and downstream sensors are not always interchangable. The 2002+ 4.0 SOHC sensors operate in different ranges, and a downstream sensor installed in an upstream hole causes problems.

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Good to know.

Now why would some one at Ford do that???
Notice I didn't say "some idiot" at Ford, trying to play nice, lol
I the late '90's AFR(air fuel ratio) sensors were starting to be used on "foreign vehicles".
These provide a current flow to describe oxygen content in exhaust, and have a wider range.
"We" have been using narrow band O2 sensors with a .1-.9 voltage change to describe oxygen content in exhaust.

They are not interchangeable since one is voltage and the other current, so computer has to be setup for one or the other.

I can see the switch to AFR as it is a better setup but why do just one sensor that way and leave the others as narrow band??
Why not just change all 3 or 4 to AFR?

And there are also NOx sensors now for Cats, Cats that store NOx and then release it after engine load is less, jeeze.
Same amount of NOx is released into the atmosphere........just better NOx numbers, less of a spike, overall.
I can see this as being an expensive fix when it goes bad.

Update

Well it must have been the fuse. I don't get the p0135 codes any more. So the O2's must be working. Now I get a P0171 and P0174 System too Lean Bank error. Any ideas?

RonD said:

Good to know.

Now why would some one at Ford do that???
Notice I didn't say "some idiot" at Ford, trying to play nice, lol

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Not a clue. All I know is that I spent two days chasing a symptom with no codes. When you were coasting to a stop, particularly down a long hill, it would try to stall out. Eventually I caught the bank 1 upstream going to 1.5V during coasting. Pulled it out, it was recently replaced, and the harness length was all wrong, but perfect for a cat monitor.

Dads Toy said:

Well it must have been the fuse. I don't get the p0135 codes any more. So the O2's must be working. Now I get a P0171 and P0174 System too Lean Bank error. Any ideas?

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Intake gaskets maybe.

Dads Toy said:

Well it must have been the fuse. I don't get the p0135 codes any more. So the O2's must be working. Now I get a P0171 and P0174 System too Lean Bank error. Any ideas?

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If both banks are lean then it is a system issue not O2.
Most common cause for those codes coming up together is MAF sensor and/or MAF air plenum leak(big tube from MAF to intake).

MAF sensor air flow sets the "0" for fuel trim, computer bases 14:1, air:fuel ratio, on that 0.
If O2 reports too little oxygen(rich) computer reduces fuel, -1
If O2 reports too much oxygen(lean) computer adds fuel, +1

If computer gets up to +20 it will set Lean code, this is to notify driver that something is wrong, computer is having to add too much fuel IF(big if) MAF sensor data is correct.

The IF is what you need to check.
Dirty MAF will under report the air coming in, so 0 is to low which is why computer has to add what it thinks is too much fuel.
Air leak in plenum or a vacuum leak is the same thing, all the air coming into the engine must go thru the MAF or computer will set the wrong 0

Now on the other side of that equation is fuel
Computer expects fuel pressure to be with in a specific range, it has no fuel pressure monitor.
If fuel pressure is low............then computer has to increase the "+" number to get enough fuel, when it gets to +20, lean code is set.

As you may have realized "Lean" or "Rich" doesn't always mean what is says, at +20 the engine may be running fine, or even -20, what it means is that computer is seeing a problem and letting you know.

+20 is not specific, it might set code if lower or higher, it is a software calculation.

Its all about the Science

Thanks RonD. That helps better understand what comes out on my OBD scanner. I'll have to look again at what I am getting to see where the trouble is. I'll start with the simple things first like vacuum leaks, clean sensor, etc..Good stuff RonD.